The present invention relates to heat exchangers and more particularly to a heat exchanger adapted for use in a high temperature and high pressure environment encountered for example in nuclear reactors. The present invention is also particularly directed toward a heat exchanger of a type having a heat exchange tube bundle formed from similar modules. The invention described herein was made in the course of or under a contract with the United States Energy Research and Development Administration.
Heat exchangers of the type contemplated by the present invention are employed in numerous applications for establishing heat exchange contact between physically separated fluids. Within such applications, a relatively high temperature primary fluid is circulated between the heat exchanger and a source of heat with a relatively low temperature secondary fluid being circulated through the heat exchanger for removing heat therefrom.
The primary and secondary fluids which are circulated through the heat exchanger may be either gases or liquids. The heat exchanger contemplated by the present invention is particularly adapted for use with gases such as helium which is commonly employed for circulation through the reactor core of high temperature gas cooled reactors. The helium circulated through the nuclear core may be considered as the relatively high temperature primary fluid. Within such reactor applications, the primary helium experiences the conditions of both very high temperature and very high pressure. Furthermore, since the primary helium fluid is circulated through the reactor core, it is also necessary to assure containment of the fluid within the reactor while avoiding its escape into the surrounding environment or auxiliary systems associted with the reactor.
At the same time, it is necessary to provide an efficient heat exchanger arrangement whereby a large contact surface area is made available for the transfer of heat from the primary fluid to the secondary fluid. This is normally accomplished with a tube bundle wherein the primary fluid may be circulated on the shell side of the bundle with the secondary fluid being circulated through the tubes. It is of course necessary within such an arrangement to provide a means for circulating the secondary fluid into and out of the tube bundle under the high temperature and pressure conditions noted above.
It is particularly important to assure complete separation between the primary and secondary fluids in the area of the tube bundle. This is difficult because of the large number of tubes and the need for forming continuous weld joints or the like at each end of each tube. Construction of the tube bundle with integral connections for the tubes to both inlet and outlet manifold means must also be performed efficiently in order to permit operating economy for the heat exchanger either within a nuclear reactor or in other applications. At the same time, at least within a nuclear reactor application, it is also desirable to be able to selectively block selected portions of the tube bundle. In the past, it has generally been necessary to exhaust the primary fluid from the reactor before access could be obtained to both the inlet and outlet manifold connections for the tube bundle.
Finally, it is important within such heat exchanger applications that the tube bundle and other components of the heat exchanger be capable of compact arrangement within regions of limited space and access. Within a nuclear reactor, the heat exchanger may be arranged within a cylindrical chamber where access is only available to the chamber from one end. Accordingly, it is desirable that both inlet and outlet means for the secondary fluid be arranged in one end of the chamber along with means for permitting access to the tube bundle, particularly the manifold means at each end thereof.
Accordingly, there has been found to remain a need for a heat exchanger including means for overcoming one or more problems of the type described above.